Differential gear.



\w. BRAY. DIFFERENTIAL GEAR.

APPLICATION FILED APR. 10 1917.

Patented Apu-1s, '1918.

l fa WyQMU WALTER IR.. BRAY, 0F MASON CITY, ILLINOIS.

DIFFERENTIAL GEAR.

Specication of Letters Patent. Patented Apr. 16, 1918,

Application led April 10, 1917. Serial No. 160,944.` i

To all 'whom t may concern.'

Be it known that I, WALTER R. DRAY, a citizen of the United States, residing at Mason City, in the county of Mason and State of Illinois, have invented a certain new and useful Improvement in Differential Gears, of which the following is a speciication.

My invention relates to drives for selfpropelled vehicles. In one of its aspects the invention is particularly useful in conne@ tion with tractors for plows or other implements where greater tractive effort is desirable on one side of the machine than the other, and in order to explain this feature I have elected to illustrate in a manner to bring out this characteristic; It will be understood by those familiar with tractive plows that in a case where one or two plowshares are employed, the plowshares are usually so located as to cause a greater drag on one side of the tractor'than the other. This is-ordinarily known as side draft. In the form of mechanism illustrated, the mechanism accommodates itself to this situation and produces greater tractive effort or torque in one of thetractor wheels than in the other. Another obj ect, and one which is not confined to the situation where greater torque is desirable in one of the vtractoi` wheels than the other, is to provide a construction wherein all the reduction and differential gear elements occupy but small compass, and wherein the number and direction of the thrusts, stresses and strains are reduced to a minimum. Another object'of the invention is to provide a construction such that the width of the individual tractor wheels may be greatly increased without increasing the distance from the outer edge of one of the wheels to the outer edge of the other. Contributory objects are concerned with certain mechanical expediente which will be hereinafter more fully described and claimed.

I accomplish my objects by the construction illustrated in the accompanying drawings, in which: V

Figure 1 is a plan view, partly in section,

of the chief operating parts of the mechanism, the motor and front wheels being indicated more or less diagrammatically.

Fig. 2 is a vertical section on the line 2'2, Fig. 1. v

Fig. 3 is a detail showing a roller pinion coperating with its crown gear, and

Fig. 4 is a diagrammatic view illustrating the principle of operation of the gearing.

Similar numerals refer to similar parts throughout the several views.

Referring to the drawings, power is furnished by the motor 1, which may assume the form of an internal combustion engine. The front wheels of the vehicle are indicated at 2, 2. The motor actuates the drive shaft 3 which preferably is provided with universal joints 4, 4. Y

Rigidly fastened to shaft 4 is a center pinion 5 which meshes with gear wheels 6. These latter are preferably three in number, as shown, and have some of the characteristics of planetary gears in that they travel around the center pinion. They are loosely mounted on studs or arbors 'Z which project from the spider 8. Said spider is rigidly fastened to and rotates the inner driven shaft 9. The rear end of this shaft is here shown to be journaled in a bearing 10 fastened to some part of the chassis or f upon the main rear axle 16. In the present` case the pinion 12 is shown in the form of a rollerpinion and gear 13 in the form of a crown gear. This form of crown gear and roller pinion is preferable in certain instances because it confines the thrust to a single direction or plane whereas if beveled gears were used the thrusts would be divided into two components arranged at an angle to each other. f

The intermediate gear 6 mesh with an internal gear 18 formed on a part 19 which is shown in the shape of a housing for the other gear wheels. Said housing has a hollow hub 20 which forms a bearing for shaft 9 and itself has a bearing in the journal'21 which is carried by some part of the chassis. A roller pinion 23 is fastened to h ub 20 and meshes with a crown gear 24 which drives the hub 25 of the other tractor wheel 26. In operation, when the driving shaft 3 is rotated, it causes the center pinion 5 to fThis "distance equals Consequently,

opposite direction. But as the pinions 12 and 23 are engaged on opposite sides, the tractor wheels both rotate in the saine direction.

But the spider exerts greater torque upon its shaft 9 than housing` 19 doesupon its" assumed that the arrow at F represents the direction and; strength of the force exerted b y the wheel 5 upon wheel 6. `Let it be assumed, also, that the wheels 5. and Gare of equal size and of a radius equal to r. To determine the strength of the` force F, let it be assumedthat the wheel 18 is held against rotation. In such event, gear wheel 6V will be temporarily fulcrumed at the point of tangency f.V The power arin through which the force F` worls will then b e the distance from. the point' of tangency s to the point f, which equals 2r. The work ariny ofthe leverage'vwill be the distance from the point f to the stud 7, which. equals 1. Hence Force :ir/:Fxag divided by a, 0i 2F.

Consequently, F equals 2F. The torque in shaft 9 will be equal to the force F multiplied by the distance between the stud v7 and shaftB. But the distance from studv 7 to shaft 3 equals 2r, hence ily fulcrunied'on the stud 7 and 4"the power arni will the distance from 8 tor'?, while the work arm will be -the distance from stud 7 to point fl As these distances are -equal, the strength of the force F" will be equal tothe strength of the force F. The torque exerted in hollow shaft 2O will be equal to the force F multiplied the distance between the pointf and 'shaft 3.

The torque in shaft20:FX3r.\-

But F equals F, and making the substitution, we have A Torque in shaft 20=I4`5X3r=3lfr Hence the torque created in shaft 9 will be 4F73 while the torque created the hollow7 shaft20 will .be r, or a ratio ofl V the crown gearsv 13V and Qt are so propon tioned they will traIlSHlitX pQW-IQ in proportion lto the torques of theiry respectiveshafts, the torque or tractive force of the tractor wheel 15 will be four-thirds as great as of tractor wheel 26. This ratio,

however, maybe modified by changing the speed ratios of said roller pinions relative to'said crown gears. It will be noted that in this construction the crown gears 13 and 24 come very GlQSe together;` and. consequently each of the tractor ivheelsmay be provided with very broad treads, there being plenty of space to extendthe width inward.` It will valso be noted that the'structur'e lends itself to assembly on the unit system, which-tends to` lower the cost of manufacture. For example, they gear wheels 5, 6,' and 18, together with their shafts and roller pinions may be assembled as alsingle unitand iiitroduced as a unit into the machine.' Also, the'l tractor wheels with theii'fhubs 'and crown gears form units, whichinav be similarly introduced. The housingr 19L Vreadily lends itself to `l forni a casing "foi" the'inclosed gea-r wheels,4 and thus theparts are well protected rin' a rsimpley and efficient manner; t

Having thus described my invention, what I cla'im as, newV and desire to secure by Iletters'Paten't, is:

1j In comb'nation, a rotating driving element, a pair of'vrot'atable driven elements Veach hali'iing its axi'spof rotation Aat an angle to tlielaxis of rotation of the'di-'iving element, and meansbetweenlthe driven' and driving' elements actuated by the latter to rotate the driven elements: with different torquesf.. .Y

2L A tractor drive comprising two tractor wheels", two coaxial rotatable driven shafts operatively connected td said wheels respectively, a driving Y,shaft Vhaving its axis of rotationf at van angle to the axis `of rotation of'y 'the driven l. shafts, and means' between Y they driven' and driving shafts actuated by a operated by said vdriving shaft for rotating the` driven shafts in opposite directions lwith different torques. Y 7 il a' et. A tractor drive comprising twoconcentricl driveny shafts, means for rotating said vshafts inv opposite directions, two tractor wheels, one on Aeachpside of said shafts,

twe: gear-connections for connecting the respective tractor wheelswith the respective shafts, said gear-connections being on opposite sides of the shafts and on the same sides as their respective tractor wheels, whereby the tractor wheels are caused to revolve both in the same direction.

5. A tractor drive comprising two coaxial driven shafts, means for rotating said shafts, in opposite directions, a pinion fastened to each of said shafts, a tractor gear wheel on one side of said shafts, meshing with one of said pinions, a second tractor gear wheel on the other side of said shafts, meshing with the other of said pinions, whereby said tractor gear wheels revolve in the same direction, and tractor wheels connected to and driven by said tractor gear wheels.

6. A tractor having two tractor wheels rotatable about a common axis, a tractor gear wheel for each of said tractor wheels, a pinion for each of said tractor gear wheels, said pinions being located between the planes of said gear wheels, two coaxial driven shafts, one of which is secured to one of said pinions and the other to the other, the driven shafts being at right angles to the axis of the tractor wheels, and means for rotating said shafts.

In witness whereof, I have hereunto subscribed my name.

VALTER R. DRAY.

Copier of thia patent may be obtained for ve cents each, by addressing the Commissioner of Patents, Washington, D. C. 

